This invention relates to an electronic switching device, such as a photo electronic switch, proximity switch or the like, which is so constructed to directly control a load connected thereto in response to an output signal generated by a detecting circuit thereof, and more particularly to an improved electronic switching device protected from any short-circuit across output terminals of the switching device.
There is well known an electronic switching device, such as a photoelectronic switch, a proximitly switch or the like, having such a construction that a switching element, e.g., thyristor or the like, is actuated by an output signal generated from a detecting circuit so as to control a power supply to an external load connected to the switching device. The conventional switching device, however, has the disadvantage that if the connected load accidentally becomes internal short or the switching device is erroneously directly connected to a power source without connecting any load in series, the switching element would be destroyed or exploded by a excessive over current flowing through the switching element on closing the same, damaging neighbor things or human body.
It is, therefore, a primary object of this invention to provide an electronic switching device including an improved protection circuit, which can directly control an external load connected thereto.
It is a further object of this invention to provide an electronic switching device which is easy and safe to be connected with the external load.
It is a still further object of this invention to provide an electronic switching device which is automatically reset to its original normal operation if a short-circuit condition is resolved after the short-circuit condition causes the switching device to be inactive.
It is another object of this invention to provide an electronic switching device having a display for indicating a normal or short-circuit condition.
According to this invention, there is provided an electronic switching device including a detection circuit or input means, a power switching element for providing a load with a switching controlled power in response to an output signal generated from the detection circuit, a current limiting means connected with the power switching element in series, and short detecting means connected with the power switching element for providing the current limiting means with a stop signal by detecting a short-circuit condition of the load.
Other objects and advantages of this invention with be apparent upon reference to the following description in conjunction with the accompanying drawings, in which: